1. Field of the Invention
This invention relates to a scanner and, more particularly, to a probe scanner for detecting coded elements in which the transmitted and received light pulses are multiplexed in a single fiber.
2. Prior Art of the Invention
Wands for reading bar codes are presently expensive and require rugged construction to withstand the usual normal handling. They typically contain light emitting diodes, photo detectors, optical components and electronic circuits which result in complexity and high cost. Inherent repeated use requires that the wand be replaced or repaired often. Accordingly, a low cost, rugged, throw-away wand would minimize maintenance and reduce the overall operating expense.
There are many hand-held probes for detecting bar codes on items in the patent literature. For example, U.S. Pat. Nos.:
3,584,779, 06/71, Kessler et al PA1 3,610,891, 10/71, Raclazek PA1 3,711,723, 01/73, McMurtry PA1 3,766,364, 10/73, Krecioch et al PA1 3,781,555, 12/73, Keefe PA1 3,869,599, 04/75, Sansone PA1 3,937,558, 02/76, Mukai et al PA1 3,947,088, 03/76, French PA1 4,027,982, 06/77, Ohishi
With one exception, each of these patents requires the use of a first fiber, or bundle of fibers, for transmitting light from the light source to the reading end of the probe and a second fiber, or bundle of fibers, for returning the reflected light from the end of the probe to the light detector. None of them disclose the use of a single fiber for carrying the light in both directions. The one exception above is the McMurtry patent assigned to the same assignee as the present application, International Business Machines Corporation. The arrangement in the McMurtry U.S. Pat. No. 3,711,723 uses a single bundle of fibers for both the transmitted and reflected light. It does not use a single fiber and the pulse generation and detection of the present invention. It uses a continuous light source as do all of the above listed patents. The McMurtry patent keeps the reflected light separated from the transmitted light by means of a rather complex optical mirror and aperture arrangement.